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Thread: Teensy 3.6

  1. #1
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    Teensy 3.6

    I have been looking for detailed documentation for teensy 3.6. I have been unable to find the pinout of the SD adaptor to modify my existing code to use it. I have a 3.2, ILI9341 with the WS2811 that controls my Christmas tree. I want to use the teensy 3.6's SD. I'm sure the documentation is close to where I have been looking. I can't locate the pins from the welcome card or the PJRC website as the 3.6 is not yet added in detail. or I'm just being lame and its obvious!

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    Take a look here or search the forum for SDIO

    https://forum.pjrc.com/threads/37652...-on-teensy-3-6

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    I see there's a 32768 hz RTC crystal on the new boards. Are there pads to connect a backup battery? Is there anything special I need to do to keep the RTC running while the rest of the board is powered off? Thanks.

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    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by plutonic View Post
    I see there's a 32768 hz RTC crystal on the new boards. Are there pads to connect a backup battery? Is there anything special I need to do to keep the RTC running while the rest of the board is powered off? Thanks.
    Yes, there is a pin you connect the + of a coin cell battery to keep the real time clock running (you would connect the - of the battery to normal ground). If you put a Teensy 3.5/3.6 on a table with the USB connector facing up, you will see a horizontal row of 5 pins just above the micro SD reader with the program button just above that. Going from left to right of the internal pins (not counting the outside row) there is:
    • Vbat: this is the pin you want to connect the + end of the battery to;
    • 3.3v: This is an alternate 3.3v pin;
    • Ground: This is an alternate ground pin;
    • Program: This pin can be used to bring out the program button outside of the Teensy. Connect to ground to get the Teensy to enter program mode;
    • Reset: This pin if connected to ground will reset the Teensy.


    Note, unlike the DS3231 real time chips, the RTC in the Teensy is not temperature compensated, so it might drift. I recall talk in the Teensy 3.0 days of somebody writing code to compensate for temperature using the internal Teensy temperature sensor (when the Teensy is powered), but I can't find it right now. Note, for Teensy 3.0, 3.1, 3.2, and LC the temperature sensor is connected to the pseudo-pin 38 with the analogRead function. In the Teensy 3.5 and 3.6, this was moved to pseudo-pin 44.

  5. #5
    Senior Member PaulStoffregen's Avatar
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    If anyone's still watching this thread, support for SDIO on Teensy 3.5 & 3.6 has been added to the Arduino SD library, as of Teensyduino 1.31-beta2.

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    Looking for a battery for the RTC on my 3.6. I see there are rechargeable Lithium batteries available for this application (https://www.amazon.com/Battery-Lithi.../dp/B005J1UC30). My question is, does the RTC circuitry on the 3.6 support charging the battery or should I be looking for something else?

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    Senior Member+ Frank B's Avatar
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    No it does not charge it.
    Why no use a simple battery ? I guess it lasts months to years..

  8. #8
    Senior Member PaulStoffregen's Avatar
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    Rechargeable batteries are a poor choice for the RTC. The main problem is their lack of ability to hold a charge for long times. Most self-discharge at room temperature on a time scale of several months.

    If you only anticipate being without power for short periods, rechargeables might seem tempting, since they can fully recharge when power returns. But even if you rarely and only lightly discharge the battery, you still don't get longevity. All batteries slowly deteriorate, even without any use. Rechargeables generally don't last as long.

    A non-rechargeable lithium coin cell really is the best choice.

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    Yes, I learned that self-discharge lesson the hard way with an altimeter I left sitting in a rocket for about four years. When I tried to charge it nothing happened. I just got done having to pay to have the battery replaced. Ouch!

    Thanks for the recommendation on the battery. Now to find a holder I can use on a solderless-breadboard.

  10. #10
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by DraconisRex View Post
    Yes, I learned that self-discharge lesson the hard way with an altimeter I left sitting in a rocket for about four years. When I tried to charge it nothing happened. I just got done having to pay to have the battery replaced. Ouch!

    Thanks for the recommendation on the battery. Now to find a holder I can use on a solderless-breadboard.
    Adafruit has these (there is an on/off version, but I suspect you don't want that) for the 20mm CR2032: https://www.adafruit.com/products/1870

    And these for the 12mm CR1220: https://www.adafruit.com/products/1868
    Last edited by MichaelMeissner; 11-01-2016 at 03:59 AM.

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